1. Field of the Invention
The present invention relates to a low-voltage excited red phosphor and a method of preparing the same, and more particularly, to a low-voltage excited red phosphor having a long lifetime for a Field Emission Display (FED) or a Vacuum Fluorescent Display (VFD), and a method of preparing the same.
2. Description of the Related Art
Low-voltage driving displays at 1 kV or less mainly include Field Emission Displays (FED), Vacuum Fluorescent Displays (VFD), etc. The Field Emission Display is actively being studied as a next generation small-sized Flat Panel Display (FPD) device, and the Vacuum Fluorescent Display (VFD) is mainly being used for a variety of display devices for household electric appliances, audio and video (AV) equipment, automobiles, etc. These low-voltage displays are constructed so that electrons emitted from an electron emitter, such as a heating wire, irradiate phosphors resulting in the production of desired images.
Phosphors for low-voltage driving devices, such as Field Emission Displays, Vacuum Fluorescent Displays, etc., should have low electrical resistance, low luminescence initiating voltages, high luminescence efficiency at low voltage, no brightness saturation, minimal defects on the phosphor particle surface, stable luminescence conditions when excited by low-velocity electrons, and they should not undergo decomposition.
Currently, a sulfide-based phosphor is widely used as a phosphor for a low-voltage driving device. As the host materials of sulfide-based phosphors have high resistance, conductive materials are added to these phosphors so that they can be used in low-velocity electron-beam excitation applications. However, non-sulfide based phosphors are actively being developed as there are problems of cathode filament contamination and phosphor efficiency deterioration due to sulfide-based gas emission and phosphor decomposition-scattering during electron-beam excitation. Additionally (ZnCd)S is an environmental contaminant.
SnO2:Eu, Y2O3:Eu, etc., are widely used red phosphors for low-voltage driving display devices, such as vacuum fluorescent display devices, field emission display devices, or the like. However, SnO2:Eu has low brightness, and Y2O3:Eu has a high driving voltage of more than 80V and insufficient conductivity so that a large amount of In2O3 as a conductive material is added, resulting in deterioration of the luminescence of the phosphor.
U.S. Pat. No. 5,619,098 discloses the red phosphor SrTiO3:Pr,Al that has an unsatisfactory improvement degree of phosphor lifetime, with a brightness maintenance level of merely 40% over 1000 hours relative to initial brightness. Therefore, a phosphor with a long lifetime is still required in the industry.
Accordingly, it is an object of the present invention to provide a low-voltage excited red phosphor having a long lifetime and a non-deteriorating high brightness.
It is another object of the present invention to provide a low-voltage excited oxide-based red phosphor having no problems of cathode filament contamination and environmental contamination.
It is yet another object of the present invention to provide a method of preparing the low-voltage excited red phosphor having the properties as above.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and other objects of the present invention are achieved by providing a low-voltage excited red phosphor comprising a matrix including an oxide of an alkaline earth metal and titanium and doping elements including a rare-earth element, a group 13 element, and Zn.
The foregoing and other objects of the present invention may also be achieved by providing a method of preparing the low-voltage excited red phosphor comprising mixing a salt of an alkaline earth metal and titanium oxide to obtain a mixture; adding a rare-earth element-containing compound, a group 13 element-containing compound, and Zn-containing compound to the mixture; and firing the mixture at a temperature in the range of 1100-1400xc2x0 C.